The following example shows how to create a FileSystemWatcher to monitor file changes (creates, deletes, renames, changes) occurring on a disk drive. The example also shows how to properly receive error notifications.

Imports System.IO
Module Module1
Sub Main()
' Create a FileSystemWatcher to monitor all files on drive C.Dim fsw AsNew FileSystemWatcher("C:\")
' Watch for changes in LastAccess and LastWrite times, and' the renaming of files or directories.
fsw.NotifyFilter = (NotifyFilters.LastAccess Or NotifyFilters.LastWrite _
Or NotifyFilters.FileName Or NotifyFilters.DirectoryName)
' Register a handler that gets called when a ' file is created, changed, or deleted.AddHandler fsw.Changed, New FileSystemEventHandler(AddressOf OnChanged)
' The commented line of code below is a shorthand of the above line.' AddHandler fsw.Changed, AddressOf OnChanged' NOTE: The shorthand version is used in the remainder of this code.' FileSystemEventHandlerAddHandler fsw.Created, AddressOf OnChanged
' FileSystemEventHandlerAddHandler fsw.Deleted, AddressOf OnChanged
' Register a handler that gets called when a file is renamed.' RenamedEventHandlerAddHandler fsw.Renamed, AddressOf OnRenamed
' Register a handler that gets called if the ' FileSystemWatcher needs to report an error.' ErrorEventHandlerAddHandler fsw.Error, AddressOf OnError
' Begin watching.
fsw.EnableRaisingEvents = True' Wait for the user to quit the program.
Console.WriteLine("Press 'Enter' to quit the sample.")
Console.ReadLine()
EndSub' This method is called when a file is created, changed, or deleted.PrivateSub OnChanged(ByVal source AsObject, ByVal e As FileSystemEventArgs)
' Show that a file has been created, changed, or deleted.Dim wct As WatcherChangeTypes = e.ChangeType
Console.WriteLine("File {0} {1}", e.FullPath, wct.ToString())
EndSub' This method is called when a file is renamed.PrivateSub OnRenamed(ByVal source AsObject, ByVal e As RenamedEventArgs)
' Show that a file has been renamed.Dim wct As WatcherChangeTypes = e.ChangeType
Console.WriteLine("File {0} {2} to {1}", e.OldFullPath, e.FullPath, wct.ToString())
EndSub' This method is called when the FileSystemWatcher detects an error.PrivateSub OnError(ByVal source AsObject, ByVal e As ErrorEventArgs)
' Show that an error has been detected.
Console.WriteLine("The FileSystemWatcher has detected an error")
' Give more information if the error is due to an internal buffer overflow.IfTypeOf e.GetException Is InternalBufferOverflowException Then' This can happen if Windows is reporting many file system events quickly ' and internal buffer of the FileSystemWatcher is not large enough to handle this' rate of events. The InternalBufferOverflowException error informs the application' that some of the file system events are being lost.
Console.WriteLine( _
"The file system watcher experienced an internal buffer overflow: " _
+ e.GetException.Message)
EndIfEndSubEndModule